Biomedical subjects

Frank Kandziora

Publications and source records attributed to Frank Kandziora.

At least 19 recordsLinked to original sources

PubMed2006

Mechanical concepts for disc regeneration.

Different strategies exist to treat intervertebral disc degeneration. Biological attempts to regenerate the disc are promising. However, degeneration of the disc is always accompanied by alterations of disc height, intradiscal pressure, load distribution, and motion patterns, respectively. Since those preconditions are independent factors for disc degeneration, it is unlikely that regeneration may occur without firstly restoring the physiological status of the affected spinal segment. In vitro and in vivo animal studies demonstrate that disc distraction normalizes intradiscal height and pressure. Furthermore, histological and radiological examinations provided some evidence for regenerative processes in the disc. Only dynamic stabilization systems currently offer the potential of a mechanical approach to intervertebral disc regeneration. Dynamic stabilization systems either using pedicle screws or with an interspinous device, demonstrate restabilization of spinal segments and reduction of intradiscal pressure. Clinical reports of patients with degenerative disc disease who underwent dynamic stabilization are promising. However, there is no evidence that those implants will lead to disc regeneration. Future treatment concepts should combine intradiscal cell based therapy together with dynamic restoration of the affected spinal segment.

Biomechanical Phenomena↗

PubMed2005

A new stand-alone anterior lumbar interbody fusion device: biomechanical comparison with established fixation techniques.

STUDY DESIGN: Established lumbar fixation methods were assessed biomechanically, and a comparison was made with a new stand-alone anterior lumbar interbody cage device incorporating integrated anterior fixation. OBJECTIVES: To compare the stability of a new stand-alone anterior implant (Test-device) with established fixation methods to assess its suitability for clinical use. Our hypothesis being that the Test-device would provide stability comparable to that provided by an anterior cage when supplemented with posterior pedicle screw fixation. SUMMARY OF BACKGROUND DATA: It is accepted that the use of rigid pedicle screw instrumentation increases the chance of achieving a solid fusion, but its use may be associated with a significant increase in postoperative morbidity caused by disruption of the posterior musculature. It is also evident that this increased fusion rate is generally not associated with increased clinical success. This dilemma has led to a search for a solution and to the development of the Test-device anterior lumbar interbody device. METHODS: The kinematic properties of either the L3-L4 or L4-L5 lumbar motion segment of 8 cadaveric lumbar spines have been tested using the following sequence of fixation: intact, Test-device, Test-device and translaminar facet screws (TS), Cage and TS, Cage and Universal Spine System (USS), and Cage and small stature USS. RESULTS: All fixation techniques except the cage and TS decreased (P < 0.05) range of motion (ROM), neutral zone (NZ), and elastic zone (EZ), and increased (P < 0.05) stiffness in comparison to the intact motion segment in all test modes. There was a significant increase (P < 0.01) in the ROM, NZ, and EZ, and decrease in the stiffness of the cage and TS group in comparison to all other stabilization techniques in flexion and rotation. There was no significant difference in the ROM, NZ, EZ, and stiffness between the Test-device and cage and USS groups in flexion, extension, and bending. The Test-device resulted in a significantly lower EZ (P < 0.05) and a significantly higher stiffness (P < 0.05) in rotation than all other fixation methods. CONCLUSIONS: The Test-device alone provided similar and the Test-device and TS higher stability than the pedicle screw constructs evaluated. These results support progression to clinical trials using the Test-device as a stand-alone implant.

Adult↗

PubMed2005

Charité total disc replacement--clinical and radiographical results after an average follow-up of 17 years.

A retrospective clinical-radiological study to evaluate the long-term outcome after artificial disc replacement was performed. The objective is to investigate long-term results after implantation of a modular type artificial disc prosthesis in patients with degenerative disc disease (DDD). Total disc replacement (TDR) is a surgical procedure intended to save segmental spinal function, and thus replace spondylodesis. Short-term results are promising, whereas long-term results are scarce. The Charité TDR is the oldest existing implant, therefore, the longest possible follow-up is presented here. Seventy-one patients were treated with 84 Charité TDRs types I-III. Indication for TDR was moderate to severe DDD. Fifty-three patients (63 TDRs) were available for long-term follow-up of 17 years. Evaluation included Oswestry disability index, visual analog scale, overall outcome score, plain and extension/flexion radiographs. Implantation of Charité TDR resulted in a 60% rate of spontaneous ankylosis after 17 years. No significant difference between the three types of prostheses was found concerning clinical outcome. Reoperation was necessary in 11% of patients. Although no adjacent segment degeneration was observed in the functional implants (17%), these patients were significantly less satisfied than those with spontaneous ankylosis. TDR, nowadays, is an approved procedure. Proof that long-term results of TDR implantation in DDD are at least as good as fusion results is still missing.

Adult↗

PubMed2005

A poly(propylene glycol-co-fumaric acid) based bone graft extender for lumbar spinal fusion: in vivo assessment in a rabbit model.

STUDY DESIGN: An animal model of posterolateral intertransverse process lumbar spinal fusion compared fusion rates amongst autologous bone (group 1), a porous, bioabsorbable, scaffold based on the biopolymer, poly(propylene glycol-co-fumaric acid) (PPF) (group 2), and a combination of autograft and the bioabsorbable scaffold (group 3). OBJECTIVES: To evaluate the feasibility of augmenting spinal fusion with an osteoconductive and bioabsorbable scaffold as an alternative or as an adjunct, i.e., an extender, to autograft. SUMMARY OF BACKGROUND DATA: There is little preclinical data on applications of bioabsorable bone graft extenders in spinal fusion. METHODS: New Zealand White rabbits underwent single-level lumbar posterolateral intertransverse process fusion. Animals were treated with one of three materials: autologous bone (group 1), a bioabsorable material based on PPF (group 2), and the PPF biopolymer scaffold with autologous bone graft (group 3). Animals were evaluated at 6 weeks, and fusion was evaluated by manual palpation, and radiographic, histologic, and histomorphometric analyses. RESULTS: Radiographic and manual palpation showed evidence of fusion in all three groups. Histomorphometric measurement of bone ingrowth showed the highest quantity of new bone in group 3 (91%), followed by group 1 (72%) and group 2 (53%). CONCLUSIONS: Results of this study suggested that osteoconductive bioabsorbable scaffolds prepared from PPF might be used as an autograft extender when applied as an adjunct to spinal fusion.

Animals↗

PubMed2005

Stress shielding in box and cylinder cervical interbody fusion cage designs.

STUDY DESIGN: A numerical analysis of stress shielding of the bone graft in box and cylinder interbody fusion cages was performed. OBJECTIVES: To evaluate the stress shielding characteristics of box and cylinder interbody fusion cages for the cervical spine with regard to their rigidity and contiguous pore size. SUMMARY OF BACKGROUND DATA: Cage design has been shown to influence loading of the augmented bone graft tissue. In addition, a large contiguous pore design is believed to be important to avoid stress shielding effects. METHODS: A two-dimensional axisymmetric, biphasic finite-element model of the cage incorporating the bone graft and the adjacent vertebral bodies was developed. Analysis was performed in two parts. First, the vertebrae were loaded by an axial compressive force, and second, the effect of vertebral penetration by the interbody cage was simulated. RESULTS: Straining of bone graft in the box cage was generally lower than that of the cylinder cage. The strains in the cylinder cage were seen to be more uniformly distributed, whereas in the box cage straining was concentrated in the graft under the endplates. Vertebral penetration by the cylinder cage resulted in significant straining of the bone graft (28% strain), whereas lower strains were determined in the box cage (a maximum of 17% strain). CONCLUSIONS: The central pore in the box design does not seem as effective as the fully open cylinder cage in transferring loads to the augmented graft tissue. Early penetration of the adjacent vertebrae by the cylinder cage may provide early postoperative stability and load the graft tissue, thereby imparting the necessary signals for fusion.

Biomechanical Phenomena↗

PubMed2005

Biomechanical testing of the lumbar facet interference screw.

STUDY DESIGN: An in vitro study was conducted to determine the biomechanical properties of a new simple, percutaneous, posterior fixation technique for the lumbar spine involving a new implant, the so-called Lumbar Facet Interference Screw. OBJECTIVES: The purpose of this study was to compare the biomechanical properties of this new fixation device with translaminar and pedicle screw fixation. SUMMARY OF BACKGROUND DATA: Several techniques were described to perform a minimal invasive posterior stabilization of the lumbar spine after an anterior lumbar interbody fusion procedure. Yet, due to the high complexity of these minimally invasive surgical procedures, currently, hardly any of these percutaneous posterior fixation techniques is carried out routinely. METHODS: Ten human lumbar spines were tested in flexion, extension, axial rotation, and lateral bending using a nonconstrained testing method. First, all motion segments were evaluated intact (group 1). After complete discectomy of L4-L5, the following stabilization techniques were tested sequentially (n = 10/group): group 2: "stand-alone" cage; group 3: cage plus translaminar screws; group 4: cage plus Lumbar Facet Interference Screw; and group 5: cage plus pedicle screws. Stiffness, ranges of motion, and neutral and elastic zones were determined. RESULTS: In comparison to the intact motion segment, the "stand-alone" cage showed a significantly higher (P < 0.05) range of motion, neutral zone, and elastic zone and a significantly lower (P < 0.05) stiffness in extension and rotation. Generally, all fixation techniques using cages plus posterior stabilization decreased range of motion, neutral zone, and elastic zone and increased stiffness in comparison to the "stand-alone" cage group. There was no significant difference between the cage plus interference screw and the cage plus translaminar screw group in all test modes. In comparison to the 2 facet joint stabilization techniques, pedicle screw stabilization decreased (P < 0.01) range of motion, neutral zone, and elastic zone and increased (P < 0.01) stiffness significantly in flexion and rotation. CONCLUSIONS: Results of this study indicate that the new Lumbar Facet Interference Screw fixation yields initial biomechanical stability similar to translaminar screw fixation, yet inferior biomechanical stability compared to pedicle screw fixation. Although these results are encouraging, additional biomechanical studies including cyclic loading tests have to evaluate the mid- and long-term stabilization capacity of this new minimally invasive fixation technique before human application.

Adult↗

PubMed2005

Treatment of traumatic cervical spine instability with interbody fusion cages: a prospective controlled study with a 2-year follow-up.

INTRODUCTION: The purpose of this prospective cohort study was to define indications and analyze the clinical and radiographic results of using interbody cages to surgically treat traumatic cervical spine instability. PATIENTS AND METHODS: 53 patients were treated by monosegmental anterior discectomy and interbody fusion using either autologous tricortical iliac crest bone graft and CSLP (cervical spine locking plate) (bone graft group, n=26) or Syncage-C filled with autologous cancellous bone grafts and CSLP (cage group n=27). Indications for surgery were traumatic cervical spine instability classified according to the AO classification as B1, B2, B3, C2, or C3. Intraoperative parameters such as blood loss and operation time were assessed. Prior to surgery and at follow-up (6,12, and 24 months), evaluation included measurement of neck pain, shoulder/arm pain, muscle strength, Neck Pain Disability Index (NPDI), and Cervical Spine Functional Score (CSFS). Neurological and overall outcome was assessed using the ASIA impairment scale and Odom's criteria, respectively. In addition, radiographic evaluation, including plain x-rays, flexion-extension views, and CT scans was performed. Fusion, segmental mobility, segmental lordosis/kyphosis and disc space height were determined. RESULTS: Operation time and hospital stay were significantly shorter (p<0.05) in the cage group than in the bone graft group. After 6,12, and 24 months there was no difference between either group in pain, muscle strength, NPDI, CSFS, neurological and overall outcome. Although the cage group showed a trend for prolonged fusion process, there was no statistically significant difference between the groups for all radiographic parameters. CONCLUSION: Under strict indications, cages offer a valid alternative to a tricortical iliac crest bone graft in the surgical treatment of monosegmental traumatic cervical spine instability. Although there was no significant difference between the cage and the bone graft group in the functional and radiographic outcome, less donor site morbidity, a shorter operating time, and a reduced hospital stay might result in cost-effectiveness of cages.

Adolescent↗

PubMed2005

Posterior stabilization of subaxial cervical spine trauma: indications and techniques.

The use of instrumentation for stabilization following cervical trauma has evolved rapidly in the past few decades. Nonoperative maneuvers, including traction, extended bed rest, and cast immobilization, have given way to wiring or screw rod constructs that allow immediate fixation and early mobilization of the patient. These procedures can be performed soon after trauma and with a minimum of surgical risk. They offer immediate stability of the injured spine, and can prevent the sequelae of acute cervical spinal cord injury that may accompany prolonged bed rest, thus allowing early rehabilitation and the potential for improved recovery. Current techniques for posterior cervical spine stabilization following trauma include spinous process or facet wiring [1-9], lateral mass plating [10-18], and cervical pedicle screws [19-27]. Several radiological tools, including MRI [28] and reformatted CT, yield precise details of the injured spine and allow the treating physician to determine which, if any, fixation technique offers the best chance of recovery with the least amount of risk. The goals of surgery following acute cervical spine injury include decompressing the injured spinal cord or nerve root, maintaining alignment, providing stability to the spine, promoting healing and fusion, and allowing early mobilization. This article will review indications for posterior cervical spine surgery, as well as the techniques that are currently available to help achieve the above-noted goals. We also report a recent retrospective review of 5-year data in treating posterior cervical trauma with lateral mass and pedicle screw fixation.

Adolescent↗

PubMed2004

Bioabsorbable interbody cages in a sheep cervical spine fusion model.

STUDY DESIGN: An experimental study using a sheep cervical spine interbody fusion model. OBJECTIVES: To compare interbody fusion of an autologous tricortical iliac crest bone graft with two bioabsorbable cages and to determine whether there are differences between the three interbody fusion techniques in 1) the ability to preserve postoperative distraction, 2) the biomechanical stability, and 3) the histologic characteristics of intervertebral bone matrix formation. SUMMARY AND BACKGROUND DATA: Bioabsorbable cages would be beneficial compared with metallic cages; however, currently no suitable bioabsorbable interbody fusion cage is available. METHOD: Twenty-four sheep underwent C3/C4 discectomy and fusion. The following stabilization techniques were used: Group 1) autologous tricortical iliac crest bone graft (n = 8); Group 2) bioabsorbable cage made of 70/30 poly(l-lactide-co-d,l-lactide) (experimental) filled with autologous cancellous bone graft (n = 8); Group 3) bioabsorbable cage made of a polymer-calciumphosphate composite (Biomet Europe, Dordrecht, The Netherlands) filled with autologous cancellous bone graft (n = 8). Radiographic scans to determine disc space height were performed before and after surgery and after 1, 2, 4, 8, and 12 weeks, respectively. After 12 weeks, animals were killed, and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans were used to assess bone mineral density, bone mineral content, and bony callus volume. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine stiffness, ROM, and neutral and elastic zone. Histomorphological and histomorphometrical analysis were performed to evaluate fusion and foreign body reactions associated with the bioabsorbable cages. RESULTS: Over a 12-week period, the polymer-calciumphosphate composite cage showed significantly higher values for disc space height compared with the bone graft and the poly(l-lactide-co-d,l-lactide) cage. Additionally, the polymer-calciumphosphate composite cage demonstrated a significantly higher stiffness and lower ROM, neutral zone, and elastic zone in axial rotation and lateral bending than any other group. However, quantitative computed tomographic scans demonstrated cracks in six of the eight polymer-calciumphosphate composite cages after 12 weeks. Histologically, the highest bone volume/total volume ratio and the highest fusion rate were found in the polymer-calciumphosphate composite cage group. Although the poly(l-lactide-co-d,l-lactide) cage showed grade I through III foreign body reactions in all fusion areas, only two animals developed grade I foreign body reactions with the polymer-calciumphosphate composite cage. CONCLUSION: After 12 weeks, there was no significant difference between the bioabsorbable poly(l-lactide-co-d,l-lactide) cage and the tricortical bone graft. In comparison to the tricortical bone graft, the bioabsorbable polymer-calciumphosphate composite cage showed significantly better distractive properties, a significantly higher biomechanical stiffness, and an advanced interbody fusion; however, six of eight polymer-calciumphosphate composite cages cracked. Although the fate of the foreign body reactions and the cracks is currently unclear for both bioabsorbable cages, the early appearance of large osteolysis associated with use of the poly(l-lactide-co-d,l-lactide) cage allows skepticism regarding the value of this bioabsorbable implant.

Absorbable Implants↗

PubMed2004

Biomechanical comparison of bioabsorbable cervical spine interbody fusion cages.

STUDY DESIGN: In vitro biomechanical study of bioabsorbable cervical spine interbody fusion cages using a sheep model. OBJECTIVES: The purpose of this study was to evaluate the segmental stability provided by 2 new developed bioabsorbable cervical spine interbody fusion cages and to compare it with a tricortical iliac crest bone graft and a titanium meshed interbody fusion cage. Further, the biomechanical effect of an additional anterior plate instrumentation was determined. SUMMARY AND BACKGROUND DATA: Despite the initial favorable results, the long-term effects of metallic cage devices on spinal motion segments are still unknown. Furthermore, shortcomings of metallic cages like migration, adjacent level degeneration, stenotic myelopathy, and artifacts in postoperative radiologic assessment have already been reported. Bioabsorbable cages have been designed to avoid these complications. Currently, no information is available about the biomechanical properties of bioabsorbable cervical spine interbody fusion cages. METHODS: Forty sheep cervical spines (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method using a nonconstrained testing apparatus. First, the motion segment C3-C4 was tested intact. After complete discectomy, the following groups were evaluated: autologous iliac crest bone graft, titanium mesh cylinder (Harms, DePuy AcroMed), bioabsorbable PDLLA-cage (experimental), and bioabsorbable Resorbon cage (Biomet Merck). Further, all implants were tested with an additional anterior plate instrumentation. The mean apparent stiffness, range of motion, neutral zone, and elastic zone were calculated from the corresponding load-displacement curves. RESULTS: No significant difference in range of motion and segmental stiffness among the tricortical iliac crest bone graft, meshed titanium Harms cage, and PDLLA-cage could be determined. The Resorbon cage significantly (P < 0.05) decreased range of motion and increased stiffness in rotation and flexion in comparisonto all tested implants and the intact motion segment. An additional anterior plate significantly (P < 0.05) decreased range of motion and increased stiffness in flexion and extension. CONCLUSION: In this study, bioabsorbable cages demonstrated biomechanical in vitro properties equal or superior to metallic cages. From the biomechanical point of view, bioabsorbable cages, especially the Resorbon cage, may be a viable alternative to current metallic interbody cage devices. However, animal experimental in vivo evaluation of bioabsorbable cervical spine interbody fusion cages still has to be performed.

Absorbable Implants↗

PubMed2004

Biomechanical comparison of expandable cages for vertebral body replacement in the thoracolumbar spine.

STUDY DESIGN: An in vitro biomechanical study of expandable cages for vertebral body replacement in the human thoracolumbar spine. OBJECTIVES: The purpose of this study was to compare the in vitro biomechanical properties of 3 different expandable cages with a nonexpandable cage. SUMMARY AND BACKGROUND DATA: Recently, there has been a rapid increase in the use and the commercial availability of expandable cages for vertebral body replacement in the thoracolumbar spine. Although all 3 expandable cages, evaluated in this study, are approved for clinical use in Europe, little information is available concerning the biomechanical properties of these implants. MATERIAL AND METHODS: Thirty-two human thoracolumbar spines (T11 to L3) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive loading technique using an unconstrained testing apparatus. Three-dimensional displacement was measured using an optical measurement system. First, all motion segments were tested intact. After complete corporectomy of L1, cages were implanted according to producer's information. The following implants (n = 8/group) were tested: 1) meshed titanium cage (nonexpandable cage, DePuy AcroMed); 2) X-tenz (expandable cage, DePuy AcroMed); 3) Synex (expandable Cage; Synthes); and 4) VBR (expandable cage, Ulrich). Finally, posterior stabilization using the Universal Spine System (Synthes), posterior-anterior stabilization using the Universal Spine System (Synthes), and anterior plating (Locking Compression Plate, Synthes) was applied to each test specimen. The mean apparent stiffness values, range of motion, and neutral and elastic zone were calculated from the corresponding load-displacement curves. RESULTS: No significant differences could be determined between the in vitro biomechanical properties of expandable and nonexpandable cages. In comparison to the intact motion segment, isolated anterior stabilization using cages and anterior plating significantly decreased stiffness and increased range of motion in all directions. In contrast, additional posterior stabilization significantly increased stiffness and decreased range of motion in all directions compared to the intact motion segment. The combined anterior-posterior stabilization demonstrated greatest stiffness results. CONCLUSION: Biomechanical results indicate that design variations of expandable cages for vertebral body replacement are of little importance. Additionally, no significant difference could be determined between the biomechanical properties of expandable and nonexpandable cages. After corporectomy, isolated implantation of expandable cages plus anterior plating was not able to restore normal stability of the motion segment. Therefore, isolated anterior stabilization using cages plus Locking Compression Plate should not be used for vertebral body replacement in the thoracolumbar spine.

Biomechanical Phenomena↗

PubMed2004

Long-term effects of local growth factor (IGF-I and TGF-beta 1) treatment on fracture healing. A safety study for using growth factors.

Previous studies showed that growth factors dramatically stimulate healing processes in bone. However, the long-term effect of locally applied growth factors on fracture healing remains unclear. In considering the safety of using growth factors, it is necessary to elucidate that after initial stimulation, the effect stops and the result is a normally healed tissue. Therefore, the purpose of the present study was to investigate the long-term time course of healing processes during growth factor (GF) stimulated and unstimulated fracture healing in a closed tibial fracture model in rats. A well established local drug delivery system was used. IGF-I (50 microg) and TGF-beta 1 (10 microg) were locally applied using a 10 microm thin polylactide (PDLLA) coating on intramedullary implants. The biomechanical and histomorphometrical results demonstrated a significant stimulation of the fracture healing due to the locally applied growth factors compared to control at days 28 and 42 in agreement with the literature. At the last time point, 84 days after fracture, no differences were measurable in the biomechanical testing and the callus composition between the groups. The callus was consistently in the late phase of remodeling with no remaining cartilage. In conclusion, local growth factor application enhances the healing in the early phase without alteration of the normal healing process.

Animals↗

PubMed2003

The initial phase of fracture healing is specifically sensitive to mechanical conditions.

Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.

Animals↗

PubMed2003

Synergistic effect of IGF-I and TGF-beta1 on fracture healing in rats: single versus combined application of IGF-I and TGF-beta1.

During the last few decades, knowledge about growth factors and their function has increased. However, little is known about the interaction of these factors during bone growth and fracture healing. In vitro studies have shown a higher rate of cell proliferation and cell metabolism after the use of IGF-I and TGF-beta1 in combination, as compared to the single use of these factors. The purpose of this study was to investigate a possible synergistic effect of these growth factors in vivo, using a fracture model. A midshaft fracture of rat tibia (n = 84) was intramedullary stabilized with poly(D,L-lactide)-coated or uncoated titanium K-wires. The growth factors IGF-I and TGF-beta1, singly or in combination, were incorporated in the coating and continuously released during fracture healing. 28 days after fracture, we performed mechanical tests and histomorphological analyses. We found a greater stimulating effect of IGF-I on fracture healing than of TGF-beta1. The combined application of both growth factors resulted in a significantly higher maximum load and torsional stiffness than the use of only one of them. The histomorphometric analyses showed an increase in remodeling of the fracture callus in this group with less cartilaginous and more mineralized tissue than in the other groups. Both growth factors seem to have a synergistic effect on fracture healing in this model.

Animals↗

PubMed2003

Biomechanical comparison of expandable cages for vertebral body replacement in the cervical spine.

OBJECT: Recently, expandable cages for vertebral body replacement in the cervical spine have been developed. The purpose of this study was to compare the biomechanical properties of expandable cages with those of a tricortical iliac crest graft and a nonexpandable cage. METHODS: Forty human cervical spines (C3-5) were tested in flexion, extension, axial rotation, and lateral bending. First all motion segments were evaluated intact. After corpectomy of C4 the spines were divided into five groups of eight and the following stabilization techniques were used: 1) autologous iliac crest bone graft; 2) mesh titanium cage; 3) anterior distraction device; 4) Synex-C titanium; and 5) Synex-C PEEK. Additionally, anterior plating and anterior plating plus posterior screw/rod fixation were applied. Stiffness, range of motion, and neutral and elastic zones were determined. In comparison with the intact motion segment all implants significantly increased stiffness in flexion and bending, but decreased stiffness in extension. There were no biomechanical differences between the nonexpandable and expandable cages. Furthermore, there were no biomechanical differences between the tricortical iliac crest graft and the cages, except for Synex-C in rotation. Additional anterior plating significantly increased biomechanical stiffness in all test modes; particularly in rotation mode, combined anterior-posterior stabilization increased stiffness by up to 102% compared with anterior plating alone. CONCLUSIONS: In comparison to a tricortical iliac crest bone graft and a nonexpandable cage, expandable cages have no biomechanical advantages. Due to the low extension and rotational stiffness, none of the implants can be recommended as a stand-alone device. Additional anterior plating increased biomechanical stability adequately. Therefore, additional posterior stabilization should only be considered in cases of severe rotational instability of the cervical spine.

Adult↗

PubMed2002

IGF-I and TGF-beta1 application by a poly-(D,L-lactide)-coated cage promotes intervertebral bone matrix formation in the sheep cervical spine.

STUDY DESIGN: A sheep cervical spine interbody fusion model was used to determine the effect of combined insulin-like growth factor-I (IGF-I) and transforming growth factor-beta-1 (TGF-beta1) applied by a poly-(D,L-lactide) (PDLLA)-coated cage. OBJECTIVES: The purpose of this study was to determine the effect of a new PDLLA carrier system, and to evaluate the effect of combined IGF-I and TGF-beta1 application in a sheep cervical spine model. SUMMARY AND BACKGROUND DATA: Growth factors such as bone morphogenic protein-2 have been shown to promote spine fusion and to overcome the disadvantages of an autologous bone graft. The optimum growth factor for promoting spinal fusion and the optimum method for delivering such growth factors are still a matter of discussion. METHOD: In this study, 32 sheep underwent C3-C4 discectomy and fusion: Group 1 (autologous tricortical iliac crest bone graft; n = 8), Group 2 (titanium cage; n = 8), Group 3 (titanium cage coated with a PDLLA carrier; n = 8), and Group 4 (titanium cage coated with a PDLLA carrier including IGF-I [5% w/w] and TGF-beta1 [1% w/w; n = 8). Blood samples, body weight, and body temperature were analyzed. Radiographic scans were performed before and after surgery, then at 1, 2, 4, 8, and 12 weeks, respectively. At the same time points, the disc space height, intervertebral angle, and lordosis angle were measured. After 12 weeks, the animals were killed, and fusion sites were evaluated using functional radiographic views of the animals in flexion and extension. Quantitative computed tomographic scans were performed to assess bone mineral density, bone mineral content, and bony callus volume. Biomechanical testing of the motion segment C3-C4 was performed in flexion, extension, axial rotation, and lateral bending. The stiffness, range of motion, neutral zone, and elastic zone were determined. Histomorphologic and histomorphometric analysis was performed, and polychrome sequential labeling was used to determine the time frame of new bone formation. RESULTS: There were no differences between the groups in terms of blood counts, body weight, and temperature. Over a 12-week period, cage Groups 2 to 4 showed significantly higher values for the intervertebral angle than for the bone graft. Functional radiographic assessment showed significantly lower residual flexion-extension movement in Group 4 than in any other group. The PDLLA-coated cages with IGF-I and TGF-beta1 showed significantly higher values for bone mineral density, bone mineral content, and bony callus volume. The average stiffness in rotation and bending was significantly higher, and the range of motion, neutral zone, and elastic zone in rotation were significantly lower in Group 4 than in any other group. Although only one animal in Group 4 demonstrated solid bony fusion after 12 weeks, histomorphometric evaluation showed a more progressed bone matrix formation in the group that had PDLLA-coated cages with IGF-I and TGF-beta1 than in any other group. Polychrome sequential labeling showed accelerated intervertebral bone matrix formation in Group 4. CONCLUSIONS: The findings showed that PDLLA coating of cervical spine interbody fusion cages as a delivery system for growth factors was effective. Although IGF-I and TGF-beta1 application by a PDLLA-coated interbody cage was not able to achieve solid bony fusion during the 12-week follow-up period, these growth factors significantly increased the results of interbody bone matrix formation. Additional longer-term studies are required to determine whether combined IGF-I and TGF-beta1 application leads to a successful spinal fusion.

Absorbable Implants↗

PubMed2002

Biomechanical analysis of biodegradable interbody fusion cages augmented With poly(propylene glycol-co-fumaric acid).

STUDY DESIGN: Three different types of biodegradable poly(L-lactide-co-D,L-lactide) cages with and without augmentation of a biodegradable poly(propylene glycol-cofumaric acid) scaffold were compared with autograft and metallic cages of the same design and size by determining the stiffness and failure load of the L4-L5 motion segment of cadaveric human spines. OBJECTIVES: To determine how these devices limit the range of motion in the lumbar spine compared with a metallic cage. If biomechanically equivalent, biodegradable spinal fusion systems ultimately could reduce local stress shielding and diminish the incidence of clinical complications, including device-related osteopenia, implant loosening, and breakage. SUMMARY OF BACKGROUND DATA: Previous studies in dogs and humans have demonstrated vertebral body osteopenia as a result of instrumented spine fusions. To the authors' knowledge, neither an in vitro nor an in vivo biomechanical analysis of a biodegradable interbody fusion system has been performed. METHODS: Forty-eight L4-L5 motion segments were isolated from 22 male and 26 female human donors with an average age of 49.6 +/- 2.7 years (range 36-55 years). Cages of similar dimensions and design, including a threaded, hollow, porous titanium BAK cage and three different BIO cages (BIO cage 1, pure polymer; BIO cage 2, polymer plus hydroxyapatite buffer; BIO cage 3, polymer plus nano-sized hydroxyapatite), produced from the same poly(L-lactide-co-D,L-lactide) polymer were tested in a comparative analysis to intact motion segment, interbody implantation of autograft, and a BIO cage augmented with an expandable biodegradable foam-scaffold fashioned from poly(propylene glycol-cofumaric acid). RESULTS: All cages were able to increase stiffness and failure load of the unstable motion segment significantly (P < 0.01). In comparison with the bone graft, the BAK cage (P < 0.01) and BIO cages 1 and 3 (P < 0.05) were able to increase stiffness and failure load. There was no significant difference between BIO cage 2 and the bone graft. Augmentation of BIO cage 1 with the foaming PPF scaffold resulted in higher stiffness and similar failure load as seen with the BAK cage. CONCLUSION: By comparison, the in vitro lumbar spinal motion segment stiffness and failure load produced by implantation of a biodegradable interbody fusion cage augmented with an expandable PPF scaffold is similar to that of the titanium BAK cage. This suggests that biodegradable anterior interbody fusion systems could be further developed for clinical applications.

Absorbable Implants↗

PubMed2002

Atlantoaxial instability in Dyggve-Melchior-Clausen syndrome. Case report and review of the literature.

Dyggve-Melchior-Clausen (DMC) syndrome is a very rare disease. Only 58 cases have been reported in the literature. The syndrome is probably an autosomal recessive inherited disorder, one that is characterized by mental retardation, the short-spine type of dwarfism, and skeletal abnormalities, especially of the spine, hands, and pelvis. Atlantoaxial instability-induced spinal cord compression is a serious and preventable complication. The purpose of this report is to describe the first case of DMC syndrome in which anterior transarticular atlantoaxial screw fixation was used to treat atlantoaxial instability. The authors report on a 17-year-old man with DMC syndrome and concomitant severe atlantoaxial instability. Computerized tomography scanning and magnetic resonance angiography demonstrated an irregular course of the vertebral artery (VA) at C-2, which made a posterior fixation procedure impossible. Additionally, transoral fusion was impossible because the patient was unable to open his mouth sufficiently. Therefore, the patient underwent anterior transarticular screw fixation. Follow-up examination 36 weeks after surgery showed solid fusion without implant failure. In conclusion, treatment of atlantoaxial instability in DMC syndrome must be considered. Specific care must be taken to determine the course of the VA. If posterior and transoral fusion are impossible, anterior transarticular atlantoaxial screw fixation might be the only alternative.

Adolescent↗